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Lap Timing for FPV Drone Racing

Lap Timing for FPV Drone Racing

FPV racing is a fast-paced sport. Split-second decisions make or break a fast run through a race course, and the difference between first and second can be fractions of a second. As in almost any type of modern racing, competitive events require reliable timing. Racing drones are harder to track than almost any other type of RC craft that have come before, so FPV racing has its own unique set of solutions. In this article we’ll discuss these specialized timing systems and help you get started with selecting one for your own race group.

FPV Race Timing Systems

There are two main components to timing race events. You need the ability to measure the time when a quadcopter passes the finish line, and a system to match the recorded times to the pilots who were flying. The former is the timing hardware, the latter is event management software. This software also helps race directors organize and run an event, acting as a database of pilots, heats, race classes, and serving up race results. Event management software brings many integrations with other systems such as publishing results to websites and providing overlays for streaming of live video.

Almost all timing systems in use today use the drone’s video transmitter (VTx) to determine its position. Since the VTx transmits on a constant frequency, differences in the signal strength for each drone can be tracked in order to determine when they are closest to timing sensors. The VTx method has proven to be a favourite for race organizers and pilots alike as no special hardware needs installed on the drone.

Choosing a Timing System

When deciding on a system, you’ll want to consider some important aspects of their performance:

  • Reliability: How often does the system miss counting laps? Is it susceptible to environmental issues like rain or heat? How difficult is it to keep running?
  • Accuracy: How accurately do the system’s times match reality? How much accuracy do you need? Honest data on the accuracy of these systems is actually very difficult to find and sometimes does not exist at all. Can you trust the published spec without knowing for sure?
  • Ease of use: How quickly can a race be set up? How much attention or maintenance is required? Is it difficult to calibrate the sensors? Will it work with the drones you fly and the environments that you fly in?
  • Race structure: Can pilots be organized into heats and classes? Can the system help with frequency management? Can it generate mains, brackets, or other schemes? Does the system provide all of the race result data the organizer needs for scoring? What conditions are available for choosing a winner (fastest lap, consecutive laps, most laps in a fixed time, etc.)
  • Added features and ecosystem: What other systems can it be used with? Scoring displays? Live streaming? Web publishing? Sound and lighting for race signaling?

With these in mind, let’s look at some solutions.

ImmersionRC LapRF 8-way and LiveTime

The ImmersionRC LapRF8-way has been the industry standard for years.

Nearly all top-tier events are run with the ImmersionRC LapRF 8-way. It’s earned a reputation for rock-solid reliability and ease of use for timing analog racing drones. Race groups often cite a near-perfect record of picking up laps once a good set of calibration values are found. There really isn’t much else that needs said: it picks up almost every lap and records those times accurately (usually within 25ms). But it’s expensive (typically $600). The LapRF 8-way is hardware only so you must connect it to an event management system from another vendor.

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One issue with the LapRF is that it doesn’t handle timing the DJI digital FPV system very well. Many organizers have difficulty with lost laps. More importantly, there are accuracy issues. In an independent test, DJI accuracy dropped to ‘usually within 160ms’ and was sometimes off by almost half a second. That’s definitely enough to throw doubt on any close finish or ‘fastest lap’ time. Many top-tier race events do not yet accept competitors running DJI FPV at all so this hasn’t become an issue at the highest levels of sport just yet, but this appears to be shifting and may become more important in the future.

User Interface for LiveTime Scoring Software
This is just one of many data-heavy screens that are part of the LiveTime software experience.

In most groups, a LapRF is handing off measurements to the LiveTime event management software. LiveTime is an established scoring system for RC vehicles and has extensive flexibility in how it can ingest, process, and output race data. For example, pilots might sign up on the MultiGP website for an event. LiveTime can download and import that registration, set the event on a schedule so race heats kick off automatically, output race results to a website in real time, and provide live overlays to connected video streaming software. To call LiveTime’s feature set extensive is an understatement, giving extreme flexibility to the organizer in how heats are structured and scored. There’s good reason this software is trusted for races with hundreds of pilots. LiveTime only runs on Windows, so you’ll need a suitable laptop in the race station. It’s available for groups of 10 or less at a free tier, and is subscription-based for larger groups or to take advantage of more features.

LiveTime owes some of its popularity to a partnership with MultiGP, for which it is an exclusive provider. Other event management systems aren’t allowed to submit times for corporate-sponsored events like the global qualifier. This sways the decision for many chapters. Nonetheless, many race directors stand furiously behind it as the best available and LiveTime staff are often seen actively interacting with the community.

Delta5 and RotorHazard

Open source timers like this Delta5 are most often built on the same bench as their owners’ race quads.

Open-source systems are the next most popular option. These generally cost only around $100, but are rarely sold fully assembled—you’ll likely need to source all of the components and build the system yourself. The Delta5 has historically been the most popular, though recently has seen few updates and closed down its Facebook support group. Another option is RotorHazard, which uses the same hardware as the Delta5 but takes a very different approach in software. Delta5 and RotorHazard can operate as both timing hardware and event management software at the same time, but they can also be used only as hardware to feed measurements into LiveTime or other compatible software.

As timing hardware, the Delta5 works very well for some organizers while others have trouble with calibration and lose as many as 10–20% of the laps. RotorHazard has an easy to understand calibration method that helps users dial in a system quickly and visually. But RotorHazard also—when used with its event management frontend—can look at historical race data and recover what would have been a missed lap. Because of this, laps are never truly lost even when a race is run on an uncalibrated system. RotorHazard also uses its hardware/software integration to correct for anomalies and delays in data transmission in ways that other systems cannot, such as accounting for network lag when running over an unstable wireless connection. In the same independent test, RotorHazard was shown to have excellent accuracy while timing analog quads (usually within 30ms), and on very tight indoor courses. RotorHazard also performed very well when timing DJI digital FPV systems, (usually within 50ms,) and this has elevated its status to the timer of choice for DJI-specific race groups.

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RotorHazard post-race marshaling and lap recovery
RotorHazard’s ability to accurately recover laps from a past race with new calibration values is considered one of its most important features.

As event management, the Delta5 is a rudimentary system with some accuracy problems that’s useful for only the most informal races. RotorHazard is far more developed here. It’s targeted toward small- and medium-sized race groups, but has been used at some large events and national championships. Race directors can organize heats, classes, and see results with a simple user interface. Pilots can be organized into classes, and results from one class can be used to seed a new set of heats in another class for the typical practice → qualifying → mains event structure. It also offers a range of the most common race format options such as ‘most laps within a fixed time’, ‘first to X laps’, ‘fastest lap’, and ‘fastest 3 consecutive laps’. While it falls short of LiveTime’s extensive feature set, RotorHazard users enjoy integrations with LED strips and panels, streaming overlays, and the ability to broadcast lap times directly into a pilot’s OSD while racing. The user interface is web-based so it’s accessible from any modern device with a web browser, and as open-source software it’s available for free.

Alternative Systems

There are quite a few other timing systems available with their own unique feature sets at various price points.

ImmersionRC LapRF Personal (the Puck)

ImmersionRC’s technology is available as a timer with just one receiver in the LapRF Personal. This is the same technology as the larger 8-way version for about $100. An Android or iOS app provides very basic race management (without multiple heats and does not save history). While the unit does have the capability to track multiple drones at once, it has poor accuracy while doing so because the receiver can only listen for one drone at a time. It’s really intended for practicing alone—and if that’s what you’re doing you’re on hardware that’s proven reliable and accurate for analog.

Chorus

The Chorus (and Chorus32) lap timers are another open-source option. The Chorus has a modular hardware design which can have just one receiver or be chained together into a larger system. Chorus is primarily controlled and managed by a phone app, though connecting to LiveTime is also possible. Chorus may be the least expensive timer in this round-up at about $16 per tracking node, so it packs a lot of value.

Chorus Lap Timer single unit
A single Chorus Lap Timer module. You can chain these together to create a timer with as few or many as you need.

VRx Modules

Several video receiver modules include lap timing functionality, including the TBS Fusion, FuriousFPV’s True-D series, and anything running the Achilles firmware. Utilizing the hardware you already have means there’s nothing to carry along with you to get your laps timed. Unfortunately, they are difficult to set up, have less than ideal reliability, and even less accuracy. No external race management systems can be used with them. While these are great to have on hand when you want to get some practice in, they are unsuitable for group racing or even serious individual time trials.

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FPV News - TBS Fusion
VRx modules that offer lap timers are great for practice but lack the features, accuracy, and reliability of competition systems.

Event Management

Alternative event management systems exist such as FPV Trackside, HydraFPV, PidFlight, and racegod. Each has a unique set of features that caters to a paticular type of organizer. If you don’t find what you’re looking for in the systems covered above, there may still be one out there that’s perfect for your group. These will require compatible timing hardware and often can connect to the LapRF 8-way or a Delta5/RotorHazard system.

TBS RaceTracker and EventTracker

At about the same time ImmersionRC introduced the LapRF systems, TBS launched its own line of timers. The RaceTracker was a personal-size timer and the EventTracker was for group races. While these were very capable pieces of equipment with good feature sets, they have been discontinued and are only minimally supported now.

Other Technologies

Scanning for video signals is the most common method for timing FPV, but a few other types have gained limited traction.

I-Lap timer set up at gate
This infrared timing system requires a vertical sensor pole placed at the finish line to watch for IR transmitters.

Infrared

Some of the first timing systems used for FPV racing were infrared detectors such as i-Lap and TrackMate. An infrared transmitter must be installed on each drone that will point in the direction of a detector when crossing the finish line. This proved to be a challenge as drones can fly through the gate in any number of unexpected angles. These systems are also affected by direct sunlight which limited their usefulness in outdoor races. Because of these and other challenges, infrared timing has largely fallen out of use with FPV drones.

RFID

Laps can be timed using onboard RFID transponders passing a detection loop, such as the MyLaps system. These are often very accurate, but they haven’t caught on in FPV racing in large part because of the expense—a MyLaps system costs well over $3000 for the event organizer. Then, each pilot’s transponder costs $100 or more. Pilots break drones often and are wary of destroying expensive transponders in the process.

Conclusion

The system that’s right for your race group depends a lot on what kind of racing you’re doing. For top-tier events with large groups on analog video, The ImmersionRC LapRF 8-way and LiveTime are the current standard, hands down. The flexibility of the software and reliability of the hardware are undisputed. Small and medium groups that don’t want all the cost and complexity, and groups that want to fly DJI digital FPV seem to be turning more toward RotorHazard. For personal practice your options grow considerably depending on how accurate you want your times to be. Hopefully this article has given you enough of a starting point, and pretty soon you’ll be off to the races.